Matrix Product States (MPS) / Tensor Networks

1D spin chain as MPS — bond dimension χ controls entanglement. SVD truncation and entropy S(L).

8
3
L = 8, χ = 3
S_max = —
S_center = —
Truncation err = 0
MPS ansatz:
|ψ⟩ = Σ A[1]^{s₁}A[2]^{s₂}…|s⟩

Area law: S(L) ~ const for gapped
Critical: S(L) ~ (c/3)log L

DMRG = variational over MPS